Notice the setting of the priority constant. If you try to use DISPATCH_QUEUE_PRIORITY_DEFAULT in the call to dispatch_get_global_queue you will get a runtime error (error #45). It appears this may be due to DISPATCH_QUEUE_PRIORITY_DEFAULT being an NSNumber and Swift wants it to be some other type and isn’t interpolating and boxing/unboxing the value. If you set the priority constant the error goes away.

Also notice that in the closure being sent to the main queue I’ve left out the ‘()->() in’ portion of the closure. It isn’t required. Swift can infer this. You could leave it out of the closure sent to the global queue too. I did it both ways for example purposes only since Swift is so new.